The electronic structure and Fermi surface of the recently discovered HgBa2Can-1CunO2n+2+δ superconductors have been determined using the full potential linear muffin-tin orbital method and precise structural information determined with neutrons by Radaelli et al. Whereas for stoichiometric HgBa2CuO4 (Hg-1201) the only band crossing the Fermi energy derived from the CuO antibonding state is half-filled, an additional HgO band that crosses EF exists in the case of HgBa2CaCu2O6 (Hg-1212) and HgBa2Ca2CuO4O8 (Hg-1223). Thus, stoichiometric HgBa2CuO4 is expected to be a Mott insulator with dopants essential for forming the normal metallic state that leads to superconductivity at 95 K, in contrast to two other members of the Hg family that are expected to be "self-doped" to a metallic normal state. As in Hg-1201, the electronic structure is two-dimensional and is dominated by van Hove singularities (vHS's) to which EF is pinned by dopants whose calculated concentration is found to agree well with that determined by Radaelli et al. for Hg-1212 for their maximum Tc = 128 K sample. Finally, predicted doping levels for stabilizing a large volume of the high-Tc Hg-1223 phase - and hence its highest Tc - are made on the basis of pinning E F to the vHS.
ASJC Scopus subject areas
- Condensed Matter Physics